1. Field of the Invention
The present invention relates to a label printing and applying machine of a portable type (which will hereafter be referred to as a "hand labeler"), and more particularly to a constant pressure printing mechanism for use with the hand labeler, by which the printing pressure is preset at a constant level within a narrow range.
2. Description of the Prior Art
In such a hand labeler, the printing head is carried by the hand operated lever, and that lever is pivotally connected to the body of the hand labeler. Through manual squeezing of the hand lever, the printing head is brought into abutment contact with the print surface of the platen, so that labels, or the like material to be printed, on the platen may be printed with desired indicia.
Since the platen of such a conventional hand labeler is fixed to the body of the hand labeler, the printing pressure of the printing head is directly dependent upon the squeezing force that is applied to the hand lever. If the hand lever is gripped with excessive squeezing force, the resultant excessive printing force cannot be damped by the platen, so that the printing head generates slight vibrations in the directions to and from the platen resulting in double printing of the labels, especially when the type surface of the printing head is made of metal. If the type surface of the printing head is made of an elastic material, on the other hand, it is crushed into abutment contact with the labels so that the ink oozes from the type surfaces onto the labels, making the resultant imprints unclear.
Since, moreover, the type of surface of the printing head is held in contact with the platen even after the printing operation until the hand lever is finally released from its squeezed condition, excessive ink will ooze out of the type surface of the printing head, if the ink is sufficiently fluid. Then, the resultant imprint is often unclear.